In the past, when it was desired to cut an opening in a sheet of plate vitreous material such as glass or mirror, a carbide-tipped drill tool bit was used. Holes were drilled through the glass in regularly spaced intervals along the perimeter of the desired opening. A groove was then scored between each adjacent hole with a hand-held diamond-tipped cutting tool. A perimeter was thus formed by the holes and grooves in the glass encompassing the material to be removed. This unwanted section of glass was then carefully broken out of the work sheet.
This very old method of making an opening in plate glass or mirrors was tedious and time consuming. The resulting opening could be jagged and uneven unless it was cut by an experienced glass cutter and/or ground smooth after breaking away the unwanted section. With this method, the entire sheet of glass could crack or break while removing the unwanted section of glass, destroying the value of costly material.
Another more recent method was to drill a first relatively large hole, then reposition the entire drilling apparatus in relation to the work surface after which a second adjacent hole of the same size is drilled. A hand glass cutting tool is then used to score a pair of tangent lines between the two holes after which the glass remaining between the holes is broken away.
There was also a problem in placing the sheet of glass to the drill press stand and holding it in place while drilling without cracking the glass. Clamps tended to hold the glass so tightly that they cracked the glass, or so loosely that the glass would shift, causing inaccuracy in the placement of the drilled holes. In U.S. Pat. No. 2,151,205, reslient suction cups were incorporated to attach the ceramic drill to the work surface, providing secure attachment to the work surface, but had to be disengaged then reattached to drill each additional hole.
A cooled, lubricated drill tool cuts through the glass faster, and leaves a neater hole. In the past, the drill bit had to be cooled while drilling manually and applying coolant against the drill bit at the work surface. Coolant had to be constantly added because the drill bit tends to disperse the coolant as it rotates.